/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: user
 * Date: 2024-03-30
 * Time: 14:06
 */
public class MyLinkedList {
     static class ListNode{
        public int val;
        ListNode prev;
        ListNode next;

         public ListNode(int val) {
             this.val = val;
         }
     }
    ListNode head;
     ListNode last;
     //头插法
    public void addFirst(int val){
        ListNode node = new ListNode(val);
        if(head == null){
            head = last = node;
        }
        else{
            node.next = head;
            head.prev = node;
            head = node;
        }
    }
    //尾插法
    public void addLast(int val){
        ListNode node = new ListNode(val);
      if(head == null){
          addFirst(val);
      }
      else{
          ListNode cur = head;
          while(cur.next != null){
              cur = cur.next;
          }
          cur.next = node;
          node.prev = cur;
          last = node;
      }
    }
    //任意位置插入,第一个数据节点为0号下标
    private ListNode findIndex(int index){
         ListNode cur = head;
        while (index != 0){
            cur = cur.next;
            index--;
        }
        return  cur;
    }
    public void addIndex(int index,int val){
        if(head == null){
            return;
        }
        if(index == 0){
            addFirst(val);
            return;
        }
        if(index == size()){
            addLast(val);
            return;
        }
        ListNode node = new ListNode(val);
           ListNode cur = findIndex(index);
           node.next = cur;
           cur.prev.next = node;
           node.prev = cur.prev;
           cur.prev = node;

    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
      if(head == null){
          return;
      }
      ListNode cur = head;
      while(cur != null){

          if(cur.val == key){
              if(cur == head){
                  head = head.next;
                  if(head != null) {
                      head.prev = null;
                  }
                  return;
              }
             else {
                  cur.prev.next = cur.next;
                  if(cur == last){
                      last = last.prev;
                  }
                  else {
                      cur.next.prev = cur.prev;
                  }
                  return;
              }
          }
          cur = cur.next;
      }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        if(head == null){
            return;
        }
        ListNode cur = head;
        while(cur != null){

            if(cur.val == key){
                if(cur == head){
                    head = head.next;
                    if(head != null) {
                        head.prev = null;
                    }
                }
                else {
                    cur.prev.next = cur.next;
                    if(cur == last){
                        last = last.prev;
                    }
                    else {
                        cur.next.prev = cur.prev;
                    }

                }
            }
            cur = cur.next;
        }
    }
    //得到带头双向链表的长度
    public int size(){
        ListNode cur = head;
        int count = 0;
        while(cur != null){
            cur = cur.next;
            count++;
        }
        return count;
    }
    //打印带头双向链表
    public void display(){
      ListNode cur = head;
      while(cur != null){
          System.out.print(cur.val+" ");
          cur = cur.next;
      }
    }
    //清空带头双向链表
    public void clear(){
        ListNode cur = head;
        while(cur != null){
            ListNode curN= cur.next;
            cur.next= null;
            cur.prev = null;
            cur = curN;
        }
        last = null;
        head = null;
    }

}
